Numbers k such that 2^(k+1) - 1 is prime.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =12a(5) =16a(6) =18a(7) =30a(8) =60a(9) =88a(10) =106a(11) =126a(12) =520a(13) =606a(14) =1278a(15) =2202a(16) =2280a(17) =3216a(18) =4252a(19) =4422a(20) =9688a(21) =9940a(22) =11212a(23) =19936a(24) =21700a(25) =23208a(26) =44496a(27) =86242a(28) =110502a(29) =132048